Preparing mayonnaise perhaps (8)
I believe the answer is:
dressing
I believe this is a double definition.
'preparing' is the first definition.
(dressing is a kind of preparing)
'mayonnaise perhaps' is the second definition.
(mayonnaise is a kind of dressing)
(Other definitions for dressing that I've seen before include "Sauce - protection for wound" , "Sauce - alignment - bandage" , "Compress" , "Sauce for salads" , "French or vinaigrette, say" .)